Embodiments of this application provide a data transmission method and a communication apparatus. The method includes: A network device sends first information to a terminal device, where the first information is used to indicate transport block size TBS configuration information and/or redundancy version RV configuration information, the TBS configuration information is used to configure a first transport block size TBS, and the RV configuration information is used to configure first RV information. The network device receives a transport block from the terminal device, or the network device sends a transport block to the terminal device, where a TBS of the transport block is the first TBS, and/or RV information of the transport block is the first RV information. The network device may expand a TBS and/or refine an RV by using the TBS configuration information and/or the RV configuration information, thereby improving a spectral efficiency when the TB is transmitted.